1. Field of the Invention
The invention relates to a light-emitting diode (LED) unit, more particularly to a flip-chip LED unit capable of producing uniform brightness.
2. Description of the Related Art
Recently, conventional light bulbs have been widely replaced by LED lighting devices in various fields due to their advantages such as low power consumption, long lifespan, etc. Conventionally, LEDs are attached to a substrate of a LED lighting unit using silver adhesives. However, the silver adhesives have relatively low thermal conductivities and low die-bonding strengths, resulting in a relatively low reliability of the LED lighting unit. Therefore, flip-chip packaging technology is adopted for the LED lighting units in order to alleviate the aforesaid shortcomings.
Nonetheless, another flaw of the conventional LED lighting unit resides in that LEDs mainly serve as point light sources due to their sizes. That is, while being applied into certain lighting devices, such as a commercial light box, poor lighting uniformity may be arise. One suggested solution is to increase the number of LEDs in the LED lighting unit for enhancing the lighting uniformity, but such approach may result in operational instability and input power losses that leads to an inefficient conversion into light energy.